The Qilian Mountains, a national key ecological function zone in Western China, play a pivotal role in ecosystem services. However, the distribution of its dominant tree species, Picea crassifolia (Qinghai spruce), ha...The Qilian Mountains, a national key ecological function zone in Western China, play a pivotal role in ecosystem services. However, the distribution of its dominant tree species, Picea crassifolia (Qinghai spruce), has decreased dramatically in the past decades due to climate change and human activity, which may have influenced its ecological functions. To restore its ecological functions, reasonable reforestation is the key measure. Many previous efforts have predicted the potential distribution of Picea crassifolia, which provides guidance on regional reforestation policy. However, all of them were performed at low spatial resolution, thus ignoring the natural characteristics of the patchy distribution of Picea crassifolia. Here, we modeled the distribution of Picea crassifolia with species distribution models at high spatial resolutions. For many models, the area under the receiver operating characteristic curve (AUC) is larger than 0.9, suggesting their excellent precision. The AUC of models at 30 m is higher than that of models at 90 m, and the current potential distribution of Picea crassifolia is more closely aligned with its actual distribution at 30 m, demonstrating that finer data resolution improves model performance. Besides, for models at 90 m resolution, annual precipitation (Bio12) played the paramount influence on the distribution of Picea crassifolia, while the aspect became the most important one at 30 m, indicating the crucial role of finer topographic data in modeling species with patchy distribution. The current distribution of Picea crassifolia was concentrated in the northern and central parts of the study area, and this pattern will be maintained under future scenarios, although some habitat loss in the central parts and gain in the eastern regions is expected owing to increasing temperatures and precipitation. Our findings can guide protective and restoration strategies for the Qilian Mountains, which would benefit regional ecological balance.展开更多
Charcoal is commonly preserved in both natural and artificial sediments,and is intensively used in paleontological,paleoenvironmental,and archaeological studies due to the abundant bio-information it contains.The bioc...Charcoal is commonly preserved in both natural and artificial sediments,and is intensively used in paleontological,paleoenvironmental,and archaeological studies due to the abundant bio-information it contains.The biochemical properties of charcoal are also used for paleoclimatic reconstruction;however,the reliability of this approach has been challenged due to a lack of clarity on how physicochemical properties change during the charring process,as well as the temperatures required for charcoalification.To address this lack,in this study,Qinghai spruce and Chinese pine wood samples from the northeastern Tibetan Plateau were heated at different temperatures and for different lengths of time under restricted oxygen conditions.The reflectance;carbon,nitrogen,and oxygen content;and tracheid morphology were quantified before and after heating to assess changes related to the charring process.Archaeological charcoal remains were then evaluated to determine the charcoalification temperatures by comparing with the experimental results.The minimum temperature required for wood charcoalification was∼300℃,while temperatures recorded by archaeological charcoal were concentrated at 400-500℃.During the charring experiments,the tracheid cell walls gradually homogenized,and tracheid cell wall thickness and lumen area decreased by∼20%.On average,50%mass losses were observed;the carbon and oxygen content(%wt.)approximately changed from 47%to 60%and 48%to 35%respectively,while the nitrogen content(%wt.)fluctuated around 0.2%.The reflectance increased slightly from 0%to 0.5%.We propose that the charcoalification of wood tissue refers to charring(in restricted air)and carbonization(in the almost absence of air)when the wood is exposed to a heat source,which then finally transforms into a black,inert solid.This quantitative study provided valuable data and a thorough assessment of the process of wood charcoalification,as well as accurately estimated the feasibility of using charcoal physicochemical properties in paleoclimatic research.展开更多
Anthropogenic greenhouse gases （GHG） emission and related global warming issues have been the focus of international communities for some time. The international communities have reached a consensus to reduce anthro...Anthropogenic greenhouse gases （GHG） emission and related global warming issues have been the focus of international communities for some time. The international communities have reached a consensus to reduce anthropogenic GHG emissions and restrain global warming. The quantitative assessment of anthropogenic GHG emissions is the scientific basis to find out the status of global GHG emission, identify the commitments of each country, and arrange the international efforts of GHG emission reduction. Currently the main assessment indicators for GHG emission include national indicator, per capita indicator, per GDP indicator, and international trade indicator etc. The introduction to the above indi- cators is put forward and their merits and demerits are analyzed. Based on the GHG emission data from the World Resource Institute （WRI）, the US Energy Information Administration （EIA）, and the Carbon Dioxide Information Analysis Center （CDIAC）, the results of each indictor are calculated for the world, for the eight G8 industrialized countries （USA, UK, Canada, Japan, Germany, France, Italy and Russia）, and the five major developing countries including China, Brazil, India, South Africa and Mexico. The paper points out that all these indicators have some limitations. The Indicator of Industrialized Accumulative Emission per Capita （IAEC） is put forward as the equitable indicator to evaluate the industrialized historical accumulative emission per capita of every country. IAEC indicator can reflect the economic achievement of GHG emission enjoyed by the current generations in every country and their commitments. The analysis of IAEC indicates that the historical accumulative emission per capita in indus- trialized countries such as UK and USA were typically higher than those of the world average and the developing countries. Emission indicator per capita per GDP, consumptive emission indicator and survival emission indicator are also put forward and discussed in the paper.展开更多
A 1000-year high-resolution(～10 years) chironomid record from varved sediments of Sugan Lake,Qaidam Basin on the northern Tibetan Plateau,is presented.The chironomid assemblages are mainly composed of the relatively ...A 1000-year high-resolution(～10 years) chironomid record from varved sediments of Sugan Lake,Qaidam Basin on the northern Tibetan Plateau,is presented.The chironomid assemblages are mainly composed of the relatively high-saline-water taxa Psectrocladius barbimanus-type and Orthocladius/Cricotopus,and the relatively low-saline-water taxa Procladius and Psectrocladius sordidellus-type.Variations in the chironomid fauna and inferred salinities suggest that over the last millennium,the Sugan Lake catchment has alternated between contrasting climatic conditions,having a dry climate during the period 990―1550 AD,a relatively humid climate during the Little Ice Age(LIA)(1550―1840 AD),and a dry climate again from 1840 AD onwards.At the decadal to centennial scale,a wet event around 1200―1230 AD,interrupting the generally arid period(990―1550 AD),and a dry event around 1590―1700 AD,punctuating the generally humid period(1550―1840 AD),are clearly documented.Trends in the chironomid-based salinity time series indicate a highly unstable climate during the LIA when salinity fluctuations were of greater magnitude and higher frequency.The effective moisture evolution in the Sugan Lake catchment during the last millennium reconstructed by chironomid analysis is in broad agreement with previous palaeo-moisture data derived from other sites in arid Northwest China(ANC).The LIA,characterized by generally humid conditions over the west-erly-dominated ANC was distinctly different from that in monsoonal China,implying an "out-of-phase" relationship between moisture evolution in these two regions during the past 1000 years.展开更多
The rise and fall of ancient cultures and civilizations is a hotly debated topic that has generated disagreements and disputes. In this paper we summarize some case studies on the abandonment of ancient sites, the pro...The rise and fall of ancient cultures and civilizations is a hotly debated topic that has generated disagreements and disputes. In this paper we summarize some case studies on the abandonment of ancient sites, the prosperity and collapse of ancient cultures, and demographic changes, as well as the influence of environment and technology during the prehistoric and historic periods. We then suggest that the dominant influencing factors for the evolution of ancient societies vary by spatial scale.At the local scale, sudden disasters are critical factors leading to the destruction and abandonment of large settlements. On a regional scale, climatic variations(e.g., droughts or cold events lasting for decades or centuries) are important factors that induce the collapse of ancient civilizations and mass migrations, while an enduring and stable optimal climate facilitated the prosperity of ancient civilizations. On a global scale, major technological innovations and their dispersion lasting for centuries and even millennia are major catalysts for population growth and social development. Lastly, we illustrate a possible mechanism under which environmental and technological factors played a critical role in ancient human survival and social evolution on different spatial scales.展开更多
Sequential samples of a 7.82-m sediment core from Genggahai Lake in the central Gonghe Basin,controlled with 12 accelerator mass spectrometry (AMS) 14 C dates,have been analysed for total organic carbon (TOC) and tota...Sequential samples of a 7.82-m sediment core from Genggahai Lake in the central Gonghe Basin,controlled with 12 accelerator mass spectrometry (AMS) 14 C dates,have been analysed for total organic carbon (TOC) and total nitrogen (TN) contents,carbon isotope of bulk organic matter (δ 13 C org),and carbonate content.Plant macrofossils and stem encrustations,derived mainly from the species of P.pectinatus,M.spicatum and Chara spp.,were identified,and they dominated the aquatic plant community of the lake.Alternations of plant macrofossils of Chara spp.and the vascular species reflect the changing productivity of the lake over time.In such a shallow lake,the carbonate content is highly related to photosynthesis of aquatic macrophytes and thus indirectly indicates variations in productivity,consistent with a quantitative estimate of palaeoproductivity.Based on these results,the palaeoproductivity history was reconstructed over the past ca.16 ka.The lake was formed or recharged at 15.3 cal ka BP,as indicated by aeolian sand deposits at the core base.A marked increase in palaeoproductivity occurred from 15.3 to 11.6 cal ka BP.Between 11.6 and 9.2 cal ka BP,a sharply increased water-level,modulated probably by the enhanced Asian summer monsoon,might have exceeded the optimum water depth for macrophyte vegetation,causing a marked decline in coverage of aquatic macrophytes and low palaeoproductivity.The palaeoproductivity appeared to be high in the early stage of the period from 9.2 to 7.4 cal ka BP,and then decreased at approximately 8.6 cal ka BP.The palaeoproductivity sustained an overall high level between 7.4 and 2.1 cal ka BP,and decreased gradually since 2.1 cal ka BP.Our results suggest that the variability of Genggahai Lake palaeoproductivity may be associated with fluctuations of the lake level controlled by the strength of the Asian summer monsoon,probably indicating changes in the Asian summer monsoon.展开更多
The Kunlun Pass Basin, located in the middle of the eastern Kunlun Mountains, received relatively continuous late Cenozoic sediments from the surrounding mountains, archiving great information to understand the deform...The Kunlun Pass Basin, located in the middle of the eastern Kunlun Mountains, received relatively continuous late Cenozoic sediments from the surrounding mountains, archiving great information to understand the deformation and uplift histories of the northern Tibetan Plateau. The Kunlun-Yellow River Movement, identified from the tectonomorphologic and sedimentary evolution of the Kunlun Pass Basin by Cui Zhijiu et al. (1997, 1998), is roughly coincident with many important global and Plateau climatic and environmental events, becoming a crucial time interval to understand tectonic-climatic interactions. However, the ages used to constrict the events remain great uncertainty. Here, we present the results of detailed magnetostratigraphy of the late Cenozoic sediments in the Kunlun Pass Basin, which show the basin sediments were formed between about 3.6 Ma and 0.5 Ma and the Kunlun-Yellow River Movement occurred at 1.2 to ～0.78 Ma. The lithology, sedimentary facies and lithofacies associations divide the basin into five stages of tectonosedimentary evolution, indicating the northern Tibetan Plateau having experienced five episodes of tectonic uplifts at ～3.6, 2.69－2.58, 1.77, 1.2, 0.87 and ～0.78 Ma since the Pliocene.展开更多
Changes in the status of freshwater resources are a topic of major global, regional and local concern. This is especially so in the arid and semi-arid regions of China, where shortage of water resources plays a crucia...Changes in the status of freshwater resources are a topic of major global, regional and local concern. This is especially so in the arid and semi-arid regions of China, where shortage of water resources plays a crucial role in limiting sustainable socioeconomic development, as well as in sustaining natural ecosystems. Recent climate change, as well as the effects of localized human activity, such as the use of water for irrigation agriculture, may have significant effects on the status of the water resources in the region. Here, we report the results of a study of changes in the areas of lakes in Gonghe Basin, northeastern Tibetan Plateau of China, over the last 60 years. The data were acquired from optical satellite images and demonstrate that the total water area of lakes in Gonghe Basin decreased significantly from the 1950s to 1980s. The cause is ascribed mainly to human activity including exploitation of farmland, against a background of increasing population; in addition, climatic data for the region demonstrate a minor drying trend during this period as the temperature increased slightly. After the construction of several reservoirs, significant amounts of water were redistributed to promote irrigation agriculture and we conclude that this caused a significant shrinkage of the natural lakes. However, both the area of farmland and the population size remained approximately constant after 1990. We conclude that the variation of the total area of lakes during the second period was mainly controlled by climatic factors （precipitation and temperature）. As the regional temperature reached a new high, the area of some of the lakes decreased sharply before finally maintaining a relatively steady state. We emphasize that anthropogenic climate change and human activity have both significantly influenced the status of water resources in the arid and semi-arid regions of China.展开更多
Changes in the hydrological processes in alpine soil constitute one of the several key problems encountered with studying watershed hydrology and ecosystem stability against the background of global warming. A typical...Changes in the hydrological processes in alpine soil constitute one of the several key problems encountered with studying watershed hydrology and ecosystem stability against the background of global warming. A typically developing thermokarst lake was chosen as a subject for a study using model simulation based on observations of soil physical properties, infiltration processes, and soil moisture. The results showed that the selected thermokarst lake imposed certain changes on the soil infiltration processes and, with the degree of impact intensifying, the initial infiltration rate decreased. The greatest reduction was achieved in the area of moderate impact. However, the stable infiltration rate and cumulative infiltration gradually increased in the surface layer at a depth of 10 and 20 cm, both decreasing initially and then increasing, which is correlated significantly with soil textures. Moreover, the cumulative infiltration changed in line with steady infiltration rate. Based on a comparative analysis, the Horton model helps better understand the effect on the soil infiltration processes of the cold alpine meadow close to the chosen thermokarst lake. In conclusion, the formation of the thermokarst lake reduced the water holding capacity of the alpine meadow soil and caused the hydraulic conductivity to increase, resulting in the reduction of runoff capacity in the area of the thermokarst lake.展开更多
On 18 January 2016,the Zhangjiazhuang high-speed railway tunnel in Ledu,Qinghai Province,China,underwent serious deformation and structural damage.A crack formed at the top of the tunnel and the concrete on the crown ...On 18 January 2016,the Zhangjiazhuang high-speed railway tunnel in Ledu,Qinghai Province,China,underwent serious deformation and structural damage.A crack formed at the top of the tunnel and the concrete on the crown peeled off.As a result,the tunnel could not be operated for three months.In order to determine the types and spatial distribution of the landslides in the region and the surface deformation characteristics associated with the tunnel deformation,we used field geological and geomorphological surveys,unmanned aerial vehicle image interpretation and differential interferometric synthetic aperture radar(D-In SAR) surface deformation monitoring.Nine ancient and old landslides were identified and analysed in the study area.Surface deformation monitoring and investigation of buildings in several villages on the slope front showed that the tunnel deformation was not related to deep-seated gravitational slope deformation.However,surface deformation monitoring revealed an active NEE–SWW fault in the area intersecting the tunnel at the location of the tunnel rupture.This constitutes a plausible mechanism for the deformation of the tunnel.Our study highlights the need for detailed engineering geomorphological investigations to better predict the occurrence of tunnel deformation events in the future.展开更多
To investigate climate evolution during the Miocene, especially during the Middle Mio- cene climate transition on the northeastern Tibetan Plateau, stable oxygen and carbon isotopes of car- bonates from a 288-m-thick ...To investigate climate evolution during the Miocene, especially during the Middle Mio- cene climate transition on the northeastern Tibetan Plateau, stable oxygen and carbon isotopes of car- bonates from a 288-m-thick lacustrine-fluvial sediment sequence covering the period from 17.1 to 6.1 Ma from Tianshui Basin, China, were analyzed. The relatively low stable oxygen isotope values indicate the prevalence of wet climate conditions during the period of 17.1-13.6 Ma, an interval corresponding to the well-known Middle Miocene Climate Optimum. The interval between 13.6 and 11.0 Ma （i.e., the late Middle Miocene） is marked by a progressive increase in the δ18O values, indicative of a decrease in precipitation, probably linked to the expansion of the East Antarctic Ice Sheet and global cooling since about 14 Ma. The climate in the study area continued to get drier as shown by the enrichment of the heavy oxygen isotope from 11 Ma. We attribute these stepwise climatic changes as revealed by our car- bonate δ18Orecord from the northeastern Tibetan Plateau to the sustained global cooling that may have reduced moist transport to Central Asia, which in turn led to a permanent aridification.展开更多
Reconstructing climate change of the last millennium is important to understand the current relationship between human-social activities and natural environmental changes. Pollen assemblages, losson-ignition(LOIo rg a...Reconstructing climate change of the last millennium is important to understand the current relationship between human-social activities and natural environmental changes. Pollen assemblages, losson-ignition(LOIo rg at 550°C), and grain size data collected from sediment core AGE15 A from the center of Anggertu lake(eastern Tengger Desert, Inner Mongolia) were used to reconstruct the regional vegetation and climate history of the last millennium. Desert or steppe desert, dominated by A rtemisia and Amaranthaceae, expanded around this region during the period of 988–1437 AD indicating a generally dry climate condition with two short humid periods(1003–1082 AD and 1388–1437 AD). These two wet periods were characterized by relatively high vegetation cover and bioproductivity, as reflected by high pollen concentrations and LOIo rg values. Increases in steppe and meadow vegetation communities(Poaceae, Cyperaceae) and vegetation cover during 1437–2015 AD suggest a wetting trend, which was also deduced from a gradual trend towards fine grains and higher lake biological productivity as reflected by LOIo rg values. An unstable lacustrine environment was identified via frequent fluctuations in pollen concentration and grain size after 1842 AD. This study also recorded a relatively dry Medieval Warm Period(MWP, 1082–1388 AD) and a wet Little Ice Age(LIA, 1437–1842 AD). Increased Amaranthaceae and high abundance of Poaceae may be related to overgrazing and agricultural activities that took place during those time periods. The evolution of vegetation in the lake region was influenced by climate change and human activities. These results could provide more fundamental support for studies of the environmental evolution of the Tengger Desert.展开更多
A 5.3 m lake core was drilled in Baahar Nuur Lake in the Ordos Plateau, and measurements of meangrain size, organic δ 13C (δ 13Corg), organic carbon content (TOC), C/N, carbonate content, carbonate δ 13C(δ 13Ccar)...A 5.3 m lake core was drilled in Baahar Nuur Lake in the Ordos Plateau, and measurements of meangrain size, organic δ 13C (δ 13Corg), organic carbon content (TOC), C/N, carbonate content, carbonate δ 13C(δ 13Ccar) and δ 18O (δ 18Ocar) were conducted for retrieving the Holocene chronosequence of climaticchanges based on 15 AMS 14C dates. The record documented four major stages of climate change inthe Ordos Plateau: (IV) a cold and dry condition before ～7.65 14C ka BP; (III) a warm and humid stagebetween ～7.65 and ～5.40 ka BP; (II) a generally drier and cooler climate since ～5.40 ka BP with twohumid events occurring from ～4.70 to ～4.60 ka BP and from ～4.20 to ～3.70 ka BP, and (I) a dry climatecharacterized by complete desiccation of the lake after 3.70 ka BP. Stage III can be further divided intothree sub-stages: (IIIa) a warm and humid episode from ～7.65 to ～6.70 ka BP, (IIIb) a warm and relativelydry episode from ～6.70 to ～6.20 ka BP, and (IIIc) the magthermal and maghumid episode of the Holo-cene from ～6.20 to ～5.40 ka BP.展开更多
Numerous large-scale fragmented bedrock landslides developed along major fault system is a world-wide phenomenon,which are often characterized with repeated reactivation throughout histories.Due to the large-scale and...Numerous large-scale fragmented bedrock landslides developed along major fault system is a world-wide phenomenon,which are often characterized with repeated reactivation throughout histories.Due to the large-scale and deep-seated features,it is normally difficult to control such landslides,which in turn pose great threat to local residents and infrastructures.Therefore,monitoring and forecasting these gigantic landslides has become a key protocol for risk reduction.This paper introduces such a typical massive landslide,named Yahuokou landslide,besides Min River in Zhouqu County,Gansu Province,China.Reactivated on July 16,2019 with a volume of approximately 4×106 m3,moving slowly and transitionally starting from top part,its toe had partially blocked the Min River and destroyed roads and houses eventually by August 11,2019.As to emergency response for such huge slowmoving landslide,there is no standard national protocols.Therefore,how to make effective emergency decision has become a challenge.Based on previous experiences,integrated multi-methods,including UAV imagery interpretation,we applied GNSS monitoring and field investigations in the early stages of landsliding,in order to assist the decisionmaking.The results show that the movement path of the current displacement is consistent with that of the 1989 reactivation event,and the slide body was separated into three relatively independent blocks with different sliding velocities and responses to rainfall.The upper and lower blocks appeared less affected by rainfall,while the middle block responded more to the changes in precipitations.It proves that the combined approaches using a variety of monitoring techniques can play an effective role in the monitoring of rapidly deformed transitional largescale landslides,and can also provide a set of reference methods for the emergency disposal of similar landslide hazards.展开更多
For almost two decades, the relationship between prehistoric natural disasters that struck the Guanting Basin in northeast Tibetan Plateau and the destruction of Lajia, an archeological site, has attracted scholarly a...For almost two decades, the relationship between prehistoric natural disasters that struck the Guanting Basin in northeast Tibetan Plateau and the destruction of Lajia, an archeological site, has attracted scholarly attention and been widely discussed. Whereas most studies have focused on the impacts of disasters on a single site within the Guanting Basin, few have examined patterns of spatiotemporal evolution of human settlements from the Neolithic to the Bronze Age. Consequently, there is a lack of clarity on the processes and mechanisms underlying the evolution of prehistoric human-land relationships in the Guanting Basin. We therefore examined spatiotemporal variations in settlements in the Guanting Basin during the period, based on the locations, altitudes, and areas of archaeological sites. We found that four sites were located on the third terrace of the Yellow River during the late Yangshao period(5500–5000 cal yr BP) and distributed within a small area. During the period between the Majiayao and Qijia cultures(5300–3600 cal yr BP), the number of sites evidently increased and the scale and distribution of settlements expanded, with settlements generally shifting toward the lower elevation areas of the Guanting Basin.During the Xindian period(3400–2700 cal yr BP), the number and scale of sites showed a downward trend and the distribution of settlements contracted. The Xindian settlement underwent altitude-based spatial differentiation, with some groups moving to areas at higher altitudes and others remained in lower altitude areas. Moreover, we found that the number, scale, and distribution range of Neolithic and Bronze Age sites in the Guanting Basin were closely related to the evolution and distribution patterns of prehistoric cultures in the regions of Gansu and Qinghai, which were further affected by climate change and agricultural development. Furthermore, there is no evidence that the altitudinal distribution pattern of Neolithic and Bronze Age settlements in the Guanting Basin was influenced by paleofloods rather it was primarily influenced by changes in subsistence strategies.展开更多
The Jilantai Salt Lake （JSL）, a lake of importance due to its salt production in China since the early Qing dynasty, is surrounded by sand dunes. Exploration of the development of these sand dunes will be helpful fo...The Jilantai Salt Lake （JSL）, a lake of importance due to its salt production in China since the early Qing dynasty, is surrounded by sand dunes. Exploration of the development of these sand dunes will be helpful for identifying the forces underlying the desert landscape and for identifying a solution to protect the salt resources. Through field investigation, we found sand dunes overlying either lacustrine and bog deposits on the lake bed at a lower altitude or littoral sediments on the higher lakeshores. Optically Stimulated Luminescence （OSL） dating results indicate that sands started to accumulate around the JSL as early as the early Holocene （around 11 ka）, while the rapid development of sand dunes occurred within the latest 0.1 ka. By comparison with climatic documents and human activities in adjacent regions, the initiation of sand accumulation around the JSL as early as the early Holocene is considered to be the result of low effective moisture in the Jilantai area. However, the rapid development of the sand dunes in the vast area surrounding the JSL was likely initiated by the intensified human activities which occurred within the latest 0.1 ka under warm and dry climatic conditions.展开更多
A pollen record from Haiyuan section in the southern part of Ningxia revealed a detailed history of vegetation variation and associated climate changes during the period from^13.0 to^7.0 14 C ka BP.A steppe landscape ...A pollen record from Haiyuan section in the southern part of Ningxia revealed a detailed history of vegetation variation and associated climate changes during the period from^13.0 to^7.0 14 C ka BP.A steppe landscape under a moderately dry(and probably cool)condition(~12.7-~12.1 14 C ka BP)was replaced by a coniferous forest dominating the landscape under a generally wet climate from^12.1 to ~11.01 4C ka BP.This generally wet period,corresponding to the European B?lling/All?rod period,can be divided into three stages:a cool and wet stage between^12.1 and^11.4 14 C ka BP,a mild and rela- tively dry stage between^11.4 and^11.2 14 C ka BP,and a mild and wet stage between^11.2 and^11.0 14 C ka BP.The coniferous forest-dominated landscape was then deteriorated into steppe landscape (~11.0-~10.6 14 C ka BP)and further into a desert steppe landscape from^10.6 to^9.8 14 C ka BP,being correspondent to the European Younger Dryas period.After a brief episode of a cool and wet climate (~9.8-~9.6 14 C ka BP),a relatively mild and dry condition prevailed during the early Holocene(~9.6- ~7.6 14 C ka BP)and then a warm and humid climate started the mid-Holocene(~7.6-~7.2 14 C ka BP).展开更多
Permafrost is an important component in hydrological processes because changes in runoff over the Arctic drainage basin cannot be well explained by changes in precipitation-related variables.However,current understand...Permafrost is an important component in hydrological processes because changes in runoff over the Arctic drainage basin cannot be well explained by changes in precipitation-related variables.However,current understanding of the influences of permafrost on hydrological dy-namics is insufficient.This study investigated historical variations in permafrost conditions and their potential hydrologic effects over the Russian Arctic drainage basin.The results show that soil temperature(at 0.40 m below surface)has increased about 1.4℃over the Ob,1.5℃over the Yenisei,and 1.8℃over the Lena River basin from 1936 through 2013,possibly resulted in a significant thawing of permafrost.Rapid active layer changes have occurred since the 1970s.The volume of the active layer increased by 28,142,and 228 km3 over the Ob,Yenisei,and Lena basins,respectively,since the 1970s.Melting ground ice caused by deepening active layer may be a limited contribution to annual runoff.Runoff during freeze season(October--April)showed significant positive correlations(p<0.05)to active layer thickness in the Yenisei and Lena basins while negative correlation(p>0.05)in the Ob basin.These results imply that,in basins with high permafrost coverage,a deeper active layer increased soil water storage capacity and perhaps contribute to an increase in winter runoff.展开更多
All around the world, ancient legends exist about the Great Flood, and the influence of the Great Flood in human evolutionary history is a hotly debated topic. In China, the legend of the prehistoric Great Flood and Y...All around the world, ancient legends exist about the Great Flood, and the influence of the Great Flood in human evolutionary history is a hotly debated topic. In China, the legend of the prehistoric Great Flood and Yu the Great's flood control has a long history and is considered to be closely linked to the establishment of the Xia Dynasty. However, there is a lack of solid scientific evidence. Against this issue, some scholars have proposed that an earthquake around 1920 BCE in the Guanting Basin along the upper reaches of the Yellow River led to the creation of a lake by damming in the Jishi Gorge and that the outburst of water from that lake led to the massive flood in the Yellow River region. These studies provided new scientific evidence for the Chinese legend. In this paper, we date skeletal samples embedded in earthquake sand blasting from the Lajia site, analyze remains from natural disasters(such as earthquakes and floods) and also archaeological remains. In addition, we compared the skeletal samples dating with that of sediments from the dammed-up lake. Our results are inconsistent with those of previous scholars. The earthquake at the Lajia site occurred no earlier than 1800 BCE, and the dammed-up lake in Jishi Gorge had disappeared by 3600 BCE. Thus, the formation and outburst of the dammed lake, the sudden death of ancient humans at the Lajia site and the ancient earthquake were independent events occurring at different times. In addition, the massive flood in the upper reaches of the Yellow River did not actually happen. Thus, we argue against and invalidate the hypothesis that the massive flood was related to Yu the Great's flood control and the establishment of the Xia Dynasty.展开更多
基金supported by the National Natural Science Foundation of China(No.42071057).
文摘The Qilian Mountains, a national key ecological function zone in Western China, play a pivotal role in ecosystem services. However, the distribution of its dominant tree species, Picea crassifolia (Qinghai spruce), has decreased dramatically in the past decades due to climate change and human activity, which may have influenced its ecological functions. To restore its ecological functions, reasonable reforestation is the key measure. Many previous efforts have predicted the potential distribution of Picea crassifolia, which provides guidance on regional reforestation policy. However, all of them were performed at low spatial resolution, thus ignoring the natural characteristics of the patchy distribution of Picea crassifolia. Here, we modeled the distribution of Picea crassifolia with species distribution models at high spatial resolutions. For many models, the area under the receiver operating characteristic curve (AUC) is larger than 0.9, suggesting their excellent precision. The AUC of models at 30 m is higher than that of models at 90 m, and the current potential distribution of Picea crassifolia is more closely aligned with its actual distribution at 30 m, demonstrating that finer data resolution improves model performance. Besides, for models at 90 m resolution, annual precipitation (Bio12) played the paramount influence on the distribution of Picea crassifolia, while the aspect became the most important one at 30 m, indicating the crucial role of finer topographic data in modeling species with patchy distribution. The current distribution of Picea crassifolia was concentrated in the northern and central parts of the study area, and this pattern will be maintained under future scenarios, although some habitat loss in the central parts and gain in the eastern regions is expected owing to increasing temperatures and precipitation. Our findings can guide protective and restoration strategies for the Qilian Mountains, which would benefit regional ecological balance.
基金This work was supported by the funding from the National Natural Science Foundation of China(41825001 and 41991251)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0601).
文摘Charcoal is commonly preserved in both natural and artificial sediments,and is intensively used in paleontological,paleoenvironmental,and archaeological studies due to the abundant bio-information it contains.The biochemical properties of charcoal are also used for paleoclimatic reconstruction;however,the reliability of this approach has been challenged due to a lack of clarity on how physicochemical properties change during the charring process,as well as the temperatures required for charcoalification.To address this lack,in this study,Qinghai spruce and Chinese pine wood samples from the northeastern Tibetan Plateau were heated at different temperatures and for different lengths of time under restricted oxygen conditions.The reflectance;carbon,nitrogen,and oxygen content;and tracheid morphology were quantified before and after heating to assess changes related to the charring process.Archaeological charcoal remains were then evaluated to determine the charcoalification temperatures by comparing with the experimental results.The minimum temperature required for wood charcoalification was∼300℃,while temperatures recorded by archaeological charcoal were concentrated at 400-500℃.During the charring experiments,the tracheid cell walls gradually homogenized,and tracheid cell wall thickness and lumen area decreased by∼20%.On average,50%mass losses were observed;the carbon and oxygen content(%wt.)approximately changed from 47%to 60%and 48%to 35%respectively,while the nitrogen content(%wt.)fluctuated around 0.2%.The reflectance increased slightly from 0%to 0.5%.We propose that the charcoalification of wood tissue refers to charring(in restricted air)and carbonization(in the almost absence of air)when the wood is exposed to a heat source,which then finally transforms into a black,inert solid.This quantitative study provided valuable data and a thorough assessment of the process of wood charcoalification,as well as accurately estimated the feasibility of using charcoal physicochemical properties in paleoclimatic research.
基金The Key Project for Knowledge Innovation Program of CAS,No.KZCX2-YW-501The Western Talent Project of CAS in2005The National S&T Pillar Program,No.007BAC03A11-05
文摘Anthropogenic greenhouse gases （GHG） emission and related global warming issues have been the focus of international communities for some time. The international communities have reached a consensus to reduce anthropogenic GHG emissions and restrain global warming. The quantitative assessment of anthropogenic GHG emissions is the scientific basis to find out the status of global GHG emission, identify the commitments of each country, and arrange the international efforts of GHG emission reduction. Currently the main assessment indicators for GHG emission include national indicator, per capita indicator, per GDP indicator, and international trade indicator etc. The introduction to the above indi- cators is put forward and their merits and demerits are analyzed. Based on the GHG emission data from the World Resource Institute （WRI）, the US Energy Information Administration （EIA）, and the Carbon Dioxide Information Analysis Center （CDIAC）, the results of each indictor are calculated for the world, for the eight G8 industrialized countries （USA, UK, Canada, Japan, Germany, France, Italy and Russia）, and the five major developing countries including China, Brazil, India, South Africa and Mexico. The paper points out that all these indicators have some limitations. The Indicator of Industrialized Accumulative Emission per Capita （IAEC） is put forward as the equitable indicator to evaluate the industrialized historical accumulative emission per capita of every country. IAEC indicator can reflect the economic achievement of GHG emission enjoyed by the current generations in every country and their commitments. The analysis of IAEC indicates that the historical accumulative emission per capita in indus- trialized countries such as UK and USA were typically higher than those of the world average and the developing countries. Emission indicator per capita per GDP, consumptive emission indicator and survival emission indicator are also put forward and discussed in the paper.
基金Supported by the Fund for Creative Research Groups,National Natural Science Foundation of China (Grant No. 40721061)Research Fund for the Doctoral Program of Higher Education (Grant No. 20060730003)
文摘A 1000-year high-resolution(～10 years) chironomid record from varved sediments of Sugan Lake,Qaidam Basin on the northern Tibetan Plateau,is presented.The chironomid assemblages are mainly composed of the relatively high-saline-water taxa Psectrocladius barbimanus-type and Orthocladius/Cricotopus,and the relatively low-saline-water taxa Procladius and Psectrocladius sordidellus-type.Variations in the chironomid fauna and inferred salinities suggest that over the last millennium,the Sugan Lake catchment has alternated between contrasting climatic conditions,having a dry climate during the period 990―1550 AD,a relatively humid climate during the Little Ice Age(LIA)(1550―1840 AD),and a dry climate again from 1840 AD onwards.At the decadal to centennial scale,a wet event around 1200―1230 AD,interrupting the generally arid period(990―1550 AD),and a dry event around 1590―1700 AD,punctuating the generally humid period(1550―1840 AD),are clearly documented.Trends in the chironomid-based salinity time series indicate a highly unstable climate during the LIA when salinity fluctuations were of greater magnitude and higher frequency.The effective moisture evolution in the Sugan Lake catchment during the last millennium reconstructed by chironomid analysis is in broad agreement with previous palaeo-moisture data derived from other sites in arid Northwest China(ANC).The LIA,characterized by generally humid conditions over the west-erly-dominated ANC was distinctly different from that in monsoonal China,implying an "out-of-phase" relationship between moisture evolution in these two regions during the past 1000 years.
基金supported by the National Natural Science Foundation of China(Grant Nos.41620104007 and 41671077)the Fundamental Research Funds for the Central Universities(Grant No.LZUJBKY-2015-k09)
文摘The rise and fall of ancient cultures and civilizations is a hotly debated topic that has generated disagreements and disputes. In this paper we summarize some case studies on the abandonment of ancient sites, the prosperity and collapse of ancient cultures, and demographic changes, as well as the influence of environment and technology during the prehistoric and historic periods. We then suggest that the dominant influencing factors for the evolution of ancient societies vary by spatial scale.At the local scale, sudden disasters are critical factors leading to the destruction and abandonment of large settlements. On a regional scale, climatic variations(e.g., droughts or cold events lasting for decades or centuries) are important factors that induce the collapse of ancient civilizations and mass migrations, while an enduring and stable optimal climate facilitated the prosperity of ancient civilizations. On a global scale, major technological innovations and their dispersion lasting for centuries and even millennia are major catalysts for population growth and social development. Lastly, we illustrate a possible mechanism under which environmental and technological factors played a critical role in ancient human survival and social evolution on different spatial scales.
基金supported by the National Natural Science Foundation of China(41021091,40830105 and 40671192)the MOE Program for New Century Excellent Talents in University and the Fundamental Research Funds for the Central Universities to Mingrui Qiang
文摘Sequential samples of a 7.82-m sediment core from Genggahai Lake in the central Gonghe Basin,controlled with 12 accelerator mass spectrometry (AMS) 14 C dates,have been analysed for total organic carbon (TOC) and total nitrogen (TN) contents,carbon isotope of bulk organic matter (δ 13 C org),and carbonate content.Plant macrofossils and stem encrustations,derived mainly from the species of P.pectinatus,M.spicatum and Chara spp.,were identified,and they dominated the aquatic plant community of the lake.Alternations of plant macrofossils of Chara spp.and the vascular species reflect the changing productivity of the lake over time.In such a shallow lake,the carbonate content is highly related to photosynthesis of aquatic macrophytes and thus indirectly indicates variations in productivity,consistent with a quantitative estimate of palaeoproductivity.Based on these results,the palaeoproductivity history was reconstructed over the past ca.16 ka.The lake was formed or recharged at 15.3 cal ka BP,as indicated by aeolian sand deposits at the core base.A marked increase in palaeoproductivity occurred from 15.3 to 11.6 cal ka BP.Between 11.6 and 9.2 cal ka BP,a sharply increased water-level,modulated probably by the enhanced Asian summer monsoon,might have exceeded the optimum water depth for macrophyte vegetation,causing a marked decline in coverage of aquatic macrophytes and low palaeoproductivity.The palaeoproductivity appeared to be high in the early stage of the period from 9.2 to 7.4 cal ka BP,and then decreased at approximately 8.6 cal ka BP.The palaeoproductivity sustained an overall high level between 7.4 and 2.1 cal ka BP,and decreased gradually since 2.1 cal ka BP.Our results suggest that the variability of Genggahai Lake palaeoproductivity may be associated with fluctuations of the lake level controlled by the strength of the Asian summer monsoon,probably indicating changes in the Asian summer monsoon.
基金This work was supported by the National Natu-ral Science Foundation of China(Grand Nos.40421101,40121303,40334038).
文摘The Kunlun Pass Basin, located in the middle of the eastern Kunlun Mountains, received relatively continuous late Cenozoic sediments from the surrounding mountains, archiving great information to understand the deformation and uplift histories of the northern Tibetan Plateau. The Kunlun-Yellow River Movement, identified from the tectonomorphologic and sedimentary evolution of the Kunlun Pass Basin by Cui Zhijiu et al. (1997, 1998), is roughly coincident with many important global and Plateau climatic and environmental events, becoming a crucial time interval to understand tectonic-climatic interactions. However, the ages used to constrict the events remain great uncertainty. Here, we present the results of detailed magnetostratigraphy of the late Cenozoic sediments in the Kunlun Pass Basin, which show the basin sediments were formed between about 3.6 Ma and 0.5 Ma and the Kunlun-Yellow River Movement occurred at 1.2 to ～0.78 Ma. The lithology, sedimentary facies and lithofacies associations divide the basin into five stages of tectonosedimentary evolution, indicating the northern Tibetan Plateau having experienced five episodes of tectonic uplifts at ～3.6, 2.69－2.58, 1.77, 1.2, 0.87 and ～0.78 Ma since the Pliocene.
基金supported by the National Natural Science Foundation of China (41372180)the Open Foundation of MOE Key Laboratory of Western China’s Environmental System,Lanzhou University and the Fundamental Research Funds for the Central Universities (lzujbky-2015-bt01)
文摘Changes in the status of freshwater resources are a topic of major global, regional and local concern. This is especially so in the arid and semi-arid regions of China, where shortage of water resources plays a crucial role in limiting sustainable socioeconomic development, as well as in sustaining natural ecosystems. Recent climate change, as well as the effects of localized human activity, such as the use of water for irrigation agriculture, may have significant effects on the status of the water resources in the region. Here, we report the results of a study of changes in the areas of lakes in Gonghe Basin, northeastern Tibetan Plateau of China, over the last 60 years. The data were acquired from optical satellite images and demonstrate that the total water area of lakes in Gonghe Basin decreased significantly from the 1950s to 1980s. The cause is ascribed mainly to human activity including exploitation of farmland, against a background of increasing population; in addition, climatic data for the region demonstrate a minor drying trend during this period as the temperature increased slightly. After the construction of several reservoirs, significant amounts of water were redistributed to promote irrigation agriculture and we conclude that this caused a significant shrinkage of the natural lakes. However, both the area of farmland and the population size remained approximately constant after 1990. We conclude that the variation of the total area of lakes during the second period was mainly controlled by climatic factors （precipitation and temperature）. As the regional temperature reached a new high, the area of some of the lakes decreased sharply before finally maintaining a relatively steady state. We emphasize that anthropogenic climate change and human activity have both significantly influenced the status of water resources in the arid and semi-arid regions of China.
基金supported by the National Natural Science Foundation of China(Grant No.41271092)the National Basic Research Program of China(Grant Nos.2010CB951402,2012CB026101)the Key Project of the National Natural Science Foundation of China(Grant No.D010102-91125010)
文摘Changes in the hydrological processes in alpine soil constitute one of the several key problems encountered with studying watershed hydrology and ecosystem stability against the background of global warming. A typically developing thermokarst lake was chosen as a subject for a study using model simulation based on observations of soil physical properties, infiltration processes, and soil moisture. The results showed that the selected thermokarst lake imposed certain changes on the soil infiltration processes and, with the degree of impact intensifying, the initial infiltration rate decreased. The greatest reduction was achieved in the area of moderate impact. However, the stable infiltration rate and cumulative infiltration gradually increased in the surface layer at a depth of 10 and 20 cm, both decreasing initially and then increasing, which is correlated significantly with soil textures. Moreover, the cumulative infiltration changed in line with steady infiltration rate. Based on a comparative analysis, the Horton model helps better understand the effect on the soil infiltration processes of the cold alpine meadow close to the chosen thermokarst lake. In conclusion, the formation of the thermokarst lake reduced the water holding capacity of the alpine meadow soil and caused the hydraulic conductivity to increase, resulting in the reduction of runoff capacity in the area of the thermokarst lake.
基金funded by the National Key Research and Development Program of China (Grant No.2018YFC1504704)the National Natural Science Foundation of China (Grant No.41661144046)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No.lzujbky-2018-k14)the Key Research and Development Program of Gansu Province (Grant No.18YF1WA114)。
文摘On 18 January 2016,the Zhangjiazhuang high-speed railway tunnel in Ledu,Qinghai Province,China,underwent serious deformation and structural damage.A crack formed at the top of the tunnel and the concrete on the crown peeled off.As a result,the tunnel could not be operated for three months.In order to determine the types and spatial distribution of the landslides in the region and the surface deformation characteristics associated with the tunnel deformation,we used field geological and geomorphological surveys,unmanned aerial vehicle image interpretation and differential interferometric synthetic aperture radar(D-In SAR) surface deformation monitoring.Nine ancient and old landslides were identified and analysed in the study area.Surface deformation monitoring and investigation of buildings in several villages on the slope front showed that the tunnel deformation was not related to deep-seated gravitational slope deformation.However,surface deformation monitoring revealed an active NEE–SWW fault in the area intersecting the tunnel at the location of the tunnel rupture.This constitutes a plausible mechanism for the deformation of the tunnel.Our study highlights the need for detailed engineering geomorphological investigations to better predict the occurrence of tunnel deformation events in the future.
基金support by the National Natural Science Foundation of China (Nos. 40721061, 40871098, 41023006, and 41072258)the National Basic Research Program of China (No. 2010CB833405)the Open Foundation of State Key Laboratory Loess and Quaternary Geology, Institute of Earth Environment, CAS (No. SKLLQG1219)
文摘To investigate climate evolution during the Miocene, especially during the Middle Mio- cene climate transition on the northeastern Tibetan Plateau, stable oxygen and carbon isotopes of car- bonates from a 288-m-thick lacustrine-fluvial sediment sequence covering the period from 17.1 to 6.1 Ma from Tianshui Basin, China, were analyzed. The relatively low stable oxygen isotope values indicate the prevalence of wet climate conditions during the period of 17.1-13.6 Ma, an interval corresponding to the well-known Middle Miocene Climate Optimum. The interval between 13.6 and 11.0 Ma （i.e., the late Middle Miocene） is marked by a progressive increase in the δ18O values, indicative of a decrease in precipitation, probably linked to the expansion of the East Antarctic Ice Sheet and global cooling since about 14 Ma. The climate in the study area continued to get drier as shown by the enrichment of the heavy oxygen isotope from 11 Ma. We attribute these stepwise climatic changes as revealed by our car- bonate δ18Orecord from the northeastern Tibetan Plateau to the sustained global cooling that may have reduced moist transport to Central Asia, which in turn led to a permanent aridification.
基金Supported by the National Natural Science Foundation of China(No.41372180)
文摘Reconstructing climate change of the last millennium is important to understand the current relationship between human-social activities and natural environmental changes. Pollen assemblages, losson-ignition(LOIo rg at 550°C), and grain size data collected from sediment core AGE15 A from the center of Anggertu lake(eastern Tengger Desert, Inner Mongolia) were used to reconstruct the regional vegetation and climate history of the last millennium. Desert or steppe desert, dominated by A rtemisia and Amaranthaceae, expanded around this region during the period of 988–1437 AD indicating a generally dry climate condition with two short humid periods(1003–1082 AD and 1388–1437 AD). These two wet periods were characterized by relatively high vegetation cover and bioproductivity, as reflected by high pollen concentrations and LOIo rg values. Increases in steppe and meadow vegetation communities(Poaceae, Cyperaceae) and vegetation cover during 1437–2015 AD suggest a wetting trend, which was also deduced from a gradual trend towards fine grains and higher lake biological productivity as reflected by LOIo rg values. An unstable lacustrine environment was identified via frequent fluctuations in pollen concentration and grain size after 1842 AD. This study also recorded a relatively dry Medieval Warm Period(MWP, 1082–1388 AD) and a wet Little Ice Age(LIA, 1437–1842 AD). Increased Amaranthaceae and high abundance of Poaceae may be related to overgrazing and agricultural activities that took place during those time periods. The evolution of vegetation in the lake region was influenced by climate change and human activities. These results could provide more fundamental support for studies of the environmental evolution of the Tengger Desert.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 40025105, 40331102, 40421101 and 40671184)US National Science Foundation (Grant No. NSF-ESH04-02509)+1 种基金Ministry of Science and Technology of China (Grant No. G2000048701)National Geographic Ministry of Society (Grant No. NGS-6938-00)
文摘A 5.3 m lake core was drilled in Baahar Nuur Lake in the Ordos Plateau, and measurements of meangrain size, organic δ 13C (δ 13Corg), organic carbon content (TOC), C/N, carbonate content, carbonate δ 13C(δ 13Ccar) and δ 18O (δ 18Ocar) were conducted for retrieving the Holocene chronosequence of climaticchanges based on 15 AMS 14C dates. The record documented four major stages of climate change inthe Ordos Plateau: (IV) a cold and dry condition before ～7.65 14C ka BP; (III) a warm and humid stagebetween ～7.65 and ～5.40 ka BP; (II) a generally drier and cooler climate since ～5.40 ka BP with twohumid events occurring from ～4.70 to ～4.60 ka BP and from ～4.20 to ～3.70 ka BP, and (I) a dry climatecharacterized by complete desiccation of the lake after 3.70 ka BP. Stage III can be further divided intothree sub-stages: (IIIa) a warm and humid episode from ～7.65 to ～6.70 ka BP, (IIIb) a warm and relativelydry episode from ～6.70 to ～6.20 ka BP, and (IIIc) the magthermal and maghumid episode of the Holo-cene from ～6.20 to ～5.40 ka BP.
基金funded by National Key Research and Development Program of China(Grant No.2017YFC1501005)the National Key R&D Program of China(Grant No.2018YFC1504704)+3 种基金the National Natural Science Foundation of China(Grant No.42007232)the Key Research and Development Program of Gansu Province(Grant No.20YF8FA074)the Science and Technology Major Project of Gansu Province(Grant No.19ZD2FA002)the Construction Project of Gansu Technological Innovation Center(Grant No.18JR2JA006)。
文摘Numerous large-scale fragmented bedrock landslides developed along major fault system is a world-wide phenomenon,which are often characterized with repeated reactivation throughout histories.Due to the large-scale and deep-seated features,it is normally difficult to control such landslides,which in turn pose great threat to local residents and infrastructures.Therefore,monitoring and forecasting these gigantic landslides has become a key protocol for risk reduction.This paper introduces such a typical massive landslide,named Yahuokou landslide,besides Min River in Zhouqu County,Gansu Province,China.Reactivated on July 16,2019 with a volume of approximately 4×106 m3,moving slowly and transitionally starting from top part,its toe had partially blocked the Min River and destroyed roads and houses eventually by August 11,2019.As to emergency response for such huge slowmoving landslide,there is no standard national protocols.Therefore,how to make effective emergency decision has become a challenge.Based on previous experiences,integrated multi-methods,including UAV imagery interpretation,we applied GNSS monitoring and field investigations in the early stages of landsliding,in order to assist the decisionmaking.The results show that the movement path of the current displacement is consistent with that of the 1989 reactivation event,and the slide body was separated into three relatively independent blocks with different sliding velocities and responses to rainfall.The upper and lower blocks appeared less affected by rainfall,while the middle block responded more to the changes in precipitations.It proves that the combined approaches using a variety of monitoring techniques can play an effective role in the monitoring of rapidly deformed transitional largescale landslides,and can also provide a set of reference methods for the emergency disposal of similar landslide hazards.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41620104007, 41671077 & 41401091)
文摘For almost two decades, the relationship between prehistoric natural disasters that struck the Guanting Basin in northeast Tibetan Plateau and the destruction of Lajia, an archeological site, has attracted scholarly attention and been widely discussed. Whereas most studies have focused on the impacts of disasters on a single site within the Guanting Basin, few have examined patterns of spatiotemporal evolution of human settlements from the Neolithic to the Bronze Age. Consequently, there is a lack of clarity on the processes and mechanisms underlying the evolution of prehistoric human-land relationships in the Guanting Basin. We therefore examined spatiotemporal variations in settlements in the Guanting Basin during the period, based on the locations, altitudes, and areas of archaeological sites. We found that four sites were located on the third terrace of the Yellow River during the late Yangshao period(5500–5000 cal yr BP) and distributed within a small area. During the period between the Majiayao and Qijia cultures(5300–3600 cal yr BP), the number of sites evidently increased and the scale and distribution of settlements expanded, with settlements generally shifting toward the lower elevation areas of the Guanting Basin.During the Xindian period(3400–2700 cal yr BP), the number and scale of sites showed a downward trend and the distribution of settlements contracted. The Xindian settlement underwent altitude-based spatial differentiation, with some groups moving to areas at higher altitudes and others remained in lower altitude areas. Moreover, we found that the number, scale, and distribution range of Neolithic and Bronze Age sites in the Guanting Basin were closely related to the evolution and distribution patterns of prehistoric cultures in the regions of Gansu and Qinghai, which were further affected by climate change and agricultural development. Furthermore, there is no evidence that the altitudinal distribution pattern of Neolithic and Bronze Age settlements in the Guanting Basin was influenced by paleofloods rather it was primarily influenced by changes in subsistence strategies.
文摘The Jilantai Salt Lake （JSL）, a lake of importance due to its salt production in China since the early Qing dynasty, is surrounded by sand dunes. Exploration of the development of these sand dunes will be helpful for identifying the forces underlying the desert landscape and for identifying a solution to protect the salt resources. Through field investigation, we found sand dunes overlying either lacustrine and bog deposits on the lake bed at a lower altitude or littoral sediments on the higher lakeshores. Optically Stimulated Luminescence （OSL） dating results indicate that sands started to accumulate around the JSL as early as the early Holocene （around 11 ka）, while the rapid development of sand dunes occurred within the latest 0.1 ka. By comparison with climatic documents and human activities in adjacent regions, the initiation of sand accumulation around the JSL as early as the early Holocene is considered to be the result of low effective moisture in the Jilantai area. However, the rapid development of the sand dunes in the vast area surrounding the JSL was likely initiated by the intensified human activities which occurred within the latest 0.1 ka under warm and dry climatic conditions.
基金Supported by the National Natural Science Foundation of China(Grant Nos.40331012 and 40421101)and NSF(Grant Nos.EAR 04-02509 and BCS 06-23478)
文摘A pollen record from Haiyuan section in the southern part of Ningxia revealed a detailed history of vegetation variation and associated climate changes during the period from^13.0 to^7.0 14 C ka BP.A steppe landscape under a moderately dry(and probably cool)condition(~12.7-~12.1 14 C ka BP)was replaced by a coniferous forest dominating the landscape under a generally wet climate from^12.1 to ~11.01 4C ka BP.This generally wet period,corresponding to the European B?lling/All?rod period,can be divided into three stages:a cool and wet stage between^12.1 and^11.4 14 C ka BP,a mild and rela- tively dry stage between^11.4 and^11.2 14 C ka BP,and a mild and wet stage between^11.2 and^11.0 14 C ka BP.The coniferous forest-dominated landscape was then deteriorated into steppe landscape (~11.0-~10.6 14 C ka BP)and further into a desert steppe landscape from^10.6 to^9.8 14 C ka BP,being correspondent to the European Younger Dryas period.After a brief episode of a cool and wet climate (~9.8-~9.6 14 C ka BP),a relatively mild and dry condition prevailed during the early Holocene(~9.6- ~7.6 14 C ka BP)and then a warm and humid climate started the mid-Holocene(~7.6-~7.2 14 C ka BP).
基金the National Key R&D Program of China(2019YFA0607003,2019YFC1509100)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20100313,XDA20100103)the National Science Foundation,United States(1503559).
文摘Permafrost is an important component in hydrological processes because changes in runoff over the Arctic drainage basin cannot be well explained by changes in precipitation-related variables.However,current understanding of the influences of permafrost on hydrological dy-namics is insufficient.This study investigated historical variations in permafrost conditions and their potential hydrologic effects over the Russian Arctic drainage basin.The results show that soil temperature(at 0.40 m below surface)has increased about 1.4℃over the Ob,1.5℃over the Yenisei,and 1.8℃over the Lena River basin from 1936 through 2013,possibly resulted in a significant thawing of permafrost.Rapid active layer changes have occurred since the 1970s.The volume of the active layer increased by 28,142,and 228 km3 over the Ob,Yenisei,and Lena basins,respectively,since the 1970s.Melting ground ice caused by deepening active layer may be a limited contribution to annual runoff.Runoff during freeze season(October--April)showed significant positive correlations(p<0.05)to active layer thickness in the Yenisei and Lena basins while negative correlation(p>0.05)in the Ob basin.These results imply that,in basins with high permafrost coverage,a deeper active layer increased soil water storage capacity and perhaps contribute to an increase in winter runoff.
基金supported by the National Natural Science Foundation of China(Grant Nos.41620104007,41671077 and41402240)
文摘All around the world, ancient legends exist about the Great Flood, and the influence of the Great Flood in human evolutionary history is a hotly debated topic. In China, the legend of the prehistoric Great Flood and Yu the Great's flood control has a long history and is considered to be closely linked to the establishment of the Xia Dynasty. However, there is a lack of solid scientific evidence. Against this issue, some scholars have proposed that an earthquake around 1920 BCE in the Guanting Basin along the upper reaches of the Yellow River led to the creation of a lake by damming in the Jishi Gorge and that the outburst of water from that lake led to the massive flood in the Yellow River region. These studies provided new scientific evidence for the Chinese legend. In this paper, we date skeletal samples embedded in earthquake sand blasting from the Lajia site, analyze remains from natural disasters(such as earthquakes and floods) and also archaeological remains. In addition, we compared the skeletal samples dating with that of sediments from the dammed-up lake. Our results are inconsistent with those of previous scholars. The earthquake at the Lajia site occurred no earlier than 1800 BCE, and the dammed-up lake in Jishi Gorge had disappeared by 3600 BCE. Thus, the formation and outburst of the dammed lake, the sudden death of ancient humans at the Lajia site and the ancient earthquake were independent events occurring at different times. In addition, the massive flood in the upper reaches of the Yellow River did not actually happen. Thus, we argue against and invalidate the hypothesis that the massive flood was related to Yu the Great's flood control and the establishment of the Xia Dynasty.
